Sunday, October 30, 2011
We're back to False Creek, this time along the north side, where the last two decades have seen an incredible transformation to park space and dense residential development. The shoreline is severely hardened - most of this edge is old fill that extends out into the historic False Creek estuary - but the seawall also provides another link in Vancouver's wonderful waterfront trail system. Variations in the height and design of the wall provide access and outlooks and interest. There have also been numerous attempts to provide some habitat, including intertidal benches, gravel and softer substrate, and even some shoreline vegetation.
I may have seen this beach from the Lion's Gate Bridge earlier, but the first time it really registered with me was 20 years ago when I heard Wolf Bauer talk about it. But this week was the first time I've actually walked it - or watched the sun set from it!
The exposure to waves from the west must drive any loose sediment on the West Vancouver shoreline eastward and historically it probably wound up incorporated into the protruding delta of the Capilano River, which emerges into Burrard Inlet just east of the bridge. Groins (groynes, in Canadian) now organize West Vancouver's sand and gravel into pocket beaches - including the large one at Ambleside Park. The beach curves out to meet a large groyne, on the end of which stands a Squamish figure welcoming visitors to Vancouver and the Squamish's historic land.
Saturday, October 29, 2011
There is a public promenade along the shoreline all the way from Dundarave to Ambleside (2-3 kms), most of it heavily armored to protect it from storm waves. The high tide prevented me from getting much of a sense of the intertidal, but it appears that the orientation, and perhaps severely limited sediment availability, results in little opportunity for real beaches except where projecting structures act as groins.
The West Vancouver Shoreline Preservation Society has been experimenting with using strategically placed rock to act as reefs to enhance habitat and to help trap sediment in the intertidal. They have also been working to improve stream mouths and stormwater outfalls along this heavily urbanized shoreline. I'll have to come back at a low tide sometime and take a closer look.
I was originally just going to do a single "West Vancouver" post, but I couldn't decide what to leave out, so I've split it into three.
It was a quick late afternoon bus trip across the Lion's Gate Bridge to West Vancouver. I got off at 25th Avenue in the Dundarave neighborhood and walked down to the beach. The beach here is limited to a beautiful little fillet on the west side of the pier (a groin/jetty, actually), swash aligned with the significant fetch from the west across the Strait of Georgia.
There was a small, lower beach against a stepped seawall in the lee of the pier, but it was mainly under the relatively high tide.
West Vancouver Shoreline Preservation Society
(I'm adding this because sometimes the location feature below links to a view that is zoomed much too far out)
The last time I visited this site was on a dreary August morning two summers ago. Today's October sunshine was a great improvement.
This is the Olympic Village site at the southeast corner of False Creek, Vancouver's urban ex-estuary. The mud flats, fringing salt marsh, and small streams have all given way to a heavily developed, and redeveloped, landscape with a steep, hardened edge. There is a longer discussion of this site in the earlier post:
False Creek: August 2010
Several of us got a great tour of the area on the eve of the Salish Sea Conference. The upland development is a world class green development with sophisticated water re-use, energy efficiencies, stormwater systems, and careful choices of buildings materials. The shoreline is a little less green than the buildings, but there are still many ecological enhancements, including the habitat island and the stream/wetland in the park that manages stormwater.
And of course, like so much of Vancouver's shoreline, the edge is a very public and a very accessible one.
I last visited this site in January 2010, only a few months after the seawall and the fill were removed and the stream mouth estuary was re-excavated. Now the site has had enough time for the vegetation to really begin to take hold. The stream has deposited a significant volume of sediment in the upper portion of the lagoon and this area is now high enough for alder to establish. The lower portions of the estuary are giving rise to various salt marsh plants. The mouth of the estuary is probably still trying to figure out how to balance the stream and the daily ebbing and flooding of the tides. On the other hand, I guess the mouths of estuaries are always trying to sort this out.
The spit itself is a pretty uneven feature. The beachface is marked by two distinct humps, perhaps an artifact of the original shoreline shape or perhaps the coarse-grained fans of earlier stream mouths. The restored spit has a low point in the berm that has been overtopped. Eventually, I expect the spit will even out a little bit, but there's not a lot of beach sediment and not a lot of wave action to move it around, so this process will be slow.
Monday, October 17, 2011
Despite its significance in shaping the modern Puget Sound landscape, the Vashon glaciation was remarkably brief (geologically) with the ice advancing and retreating across the southern Lowland in a thousand years, perhaps much less. Saturday's field trip looked at a fascinating legacy of the rapid recession.
As the ice melted northwards towards Tacoma, it may have trapped meltwater in a large lake beneath the ice in what is now the Puyallup Valley. When the pressure got high enough, the water burst out through spillways on the western edge of the valley and poured across Lakewood and Steilacoom, eroding and redepositing enormous volumes of gravel in a complex pattern of broad channels and terraces. LIDAR images capture a remarkable fluvial landscape stretching across the Lakewood and Steilacoom area, one not fully appreciated when stuck in Fort Lewis traffic on I-5.
The outburst floods (Jokulhaups), of which there were many, reached Lake Russell (the glacial lake that occupied South Puget Sound at that time) at Dupont and later near the mouth of Chambers Creek, where they formed large, steep, coarse-grained deltas. The tops of the deltas are 160-200 feet above the modern shoreline, corresponding to the level of Lake Russell.
Much of 20th-Century Seattle and Tacoma were built from sand and gravel mined from the Chambers Creek delta, but that pit ran out of room to grow and has been replaced by a park and a golf course (Pioneer: October 2010). Since then, the region has built its foundations and its roads and its bridges with aggregate from this paleo-delta in Dupont (aerial image), which lies just north of Sequalitchew Creek.
Present three dozen geologists with a 160' cliff of gravel foreset beds and they all get pretty excited. The afternoon sun was warming the gravel face and we were entertained by a near constant rain of pebbles. It was probably a good thing we weren't allowed to actually inspect the face carefully - we might have lost someone under a large pile of clean gravel. On the other hand, it would have been interesting to look more closely for clues as to how quickly this delta originally formed.
It was great that the folks from CalPortland were willing to show us around. Credit for the day goes to Kathy and Darrell and Matthew, who've put together a great story and led a great trip.
Sunday, October 16, 2011
If the Puget Sound shoreline has a start and an end, this would be Mile 0, at least for those of us who think from left to right (and who consider PS to include entire U.S. portion of the Salish Sea). It is also Mile 0 of the 49th parallel, at least the part of it that forms the boundary between the U.S. and Canada. It's a straight shot from here east to the Lake of the Woods (Minnesota/Manitoba).
The big trees on the bluff (which are nicely displayed on the trail down to the beach) suggest this bluff isn't eroding terribly fast. The beach to the south had a fairly wide berm (consistent with the slow bluff erosion).
I've noted before that this beach is one where it is possible the net drift direction has changed due to the construction of the ferry terminal and causeway on Roberts Bank, which forms a pretty effective breakwater for storm waves coming down the Strait of Georgia, although it's not clear to me what effect that would have on a straight stretch of beach like this.
I visited this same beach from the north several years ago (49th Parallel: August 2007). In both cases, I didn't wander too far across the line.
Lily Point itself is a low cuspate foreland (recurved spit?), but the bluffs that surround it are high and steep. The south bluff contains a large deep-seated landslide (Lily Point: August 2011), whereas the north bluff is a simpler, but even more spectacular cliff of either glacial outwash or older fluvial sediments (paleo-Fraser River??), although I suspect the story is more complicated than that.
This bluff dumps an awful lot of sand onto the beach - and the beach to the north widens quickly to form a small barrier. Two miles north, after another section of cliffs, this beach becomes the Maple Beach described in the previous post.
At low tide, one can practically walk across Boundary Bay on the sand flats, but at high tide the water comes right up to the seawall. The upper beach and the berm of this sand spit is long gone beneath the roadway, although in recent years, nourishment has been used to rebuild the beach and provide protection to the wall itself.
Maple Beach: August 2006
The beach derives much of its coarse sediment from the bluffs at Lily Point south of here. And this beach is just the base of a much larger system of historic and modern spits that extends north across the border to Centennial Beach and Beach Grove in Tsawwassen.
The "C" on the marker might stand for Canada, although I suspect it does not. The border is a bit of a groin and the seawalls are just as impressive north of the border as south.
This wraps up our tour of pocket beaches along the Myrtle Edwards shoreline. This is the best known and the best documented and I've posted shots of it before. I still love the way this beach attracts people, both physically and visually. It's a nice contrast to the seawall to the south and the riprap to the north. It's also an interesting contrast to the two nearby pocket beaches described in the previous posts.